No loving parent sets out to raise an unhappy and unhealthy child, but that's exactly what many mothers and fathers are doing, and they may not even realize it. Almost nine million American children and teenagers weigh more than they should. That's three times as many as a generation ago.

The three young people in this story decided to share their struggle to lose weight with each other and with Dateline. This summer they are determined. They'd better be. It's their third summer in a row at Camp La Jolla, a fitness summer camp just north of San Diego.

It’s an increasingly familiar American struggle and one of the most difficult: three teenagers, desperate to lose weight. And this is not just about counting calories. It's about confronting their lives, their parents, themselves, and coming of age in an era of abundance.

Justin Rogers: “My name is Justin Rogers. I'm from Guthrie, Oklahoma. I play the guitar and the harmonica and the mandolin.”

Justin, 17, looks and acts much older than he is.

Justin: “I think overweight people, they either get really social, or really withdrawn. And I'm the kind that is really social. Luckily, you know?”

But Justin's obvious intelligence and maturity have not extended to good judgement about food.

Justin: “Honestly, I'm just compulsive. You know. I go, I'd just be kind of bored and walking there to the refrigerator, and just open it up. Go through leftovers or something.”

And a hectic home has not made it any easier. Genetics can be cruel. Justin grew up the only overweight child in his family. His five brothers and sisters are rake thin. They can eat whatever they want. But in this crowded house, it's been a lonely battle for Justin.

Justin: “We try to eat right, but we have a real busy schedule. So the fast food just kills us.”

If Justin has been the victim of a supportive environment, for his camp roommate it's been the opposite problem.

Anthony Chavez, or TJ, from Yuba City, Northern California is 17 years old.

TJ Chavez: ‘My mom and dad broke up when I was just going into my sixth grade year. And that's like when I really started putting on weight. I remember just eating, eating constantly.”

Morrison: “Why do you think then?”

TJ: “Probably because I was sad. “

Mom left dad and took TJ with her, and from then on, TJ'S mother became his only ally, and his closest friend.

Natalina Guerra: “We did everything together. Everything. It was just me and TJ. I wanted to make him happy.”

TJ: “I think my mom would feel bad for me. And she'd just go buy me more and more food. And that wouldn't help me at all… There's this thing in my town. It's like a one-pound hamburger. It's like one pound of cheese and everything and mayonnaise. And I had two of those just for dinner.“

By the time he was 12, TJ was almost 400 pounds.

TJ: “I used to get made fun of a lot, a lot. I remember it.”

Morrison: “It still bothers you, doesn't it?”

TJ: “Oh, yes. It always bothered me. I think it always will.”

Morrison: “What was the worst?”

TJ: “When I used to go to sixth, seventh and eighth grade dances and used to ask a girl to dance, and she'd go, ‘not with you.’”

Morrison: “Could you see how it was bothering him?”

Natalina Guerra: “Yeah. He searched for more food because that was his comfort zone. And you know, there he went never ending circle.”

Morrison: “But then you see it happen to your only son. Kind of live it twice.”

Video: More children face weighty issue
Nanette Garcia is 15, from San Diego, and also lives with her divorced mom. But for these two food isn't a joint comfort. In recent years, it's been more like a battleground. Nanette's mother works long hours, far from home, leaving Nanette alone for most weekday meals. It’s an increasingly familiar American problem.

Obesity, especially begun so young, has consequences. By second grade, Nanette had developed insulin resistance. She must now take medication to stave off type 2 diabetes, a crippling disease once seen only in adults, but now epidemic among overweight teens. Nanette feels frightened, alone, and depressed.

Nanette Garcia: “If I'm in a depressed mood I'll eat just to get away for a little while. You know, I gain more weight. That's even worse. And then like I'll just fall into like a black hole of depression.”

Nanette's doctor, Jeff Schwimmer from Children's Hospital San Diego, made national news last year when he published a study arguing that obese children have a quality of life as low as children with cancer, undergoing chemotherapy. Dr. Schwimmer compared factors like mood, self esteem, and daily functioning.

Dr. Jeff Schwimmer: “One of the things that also struck us was the number of days of school missed by these children.”

They miss more than quadruple the days missed by their thinner peers. Medical complications of obesity can reduce average life expectancy by up to 20 years. But Dr. Schwimmer thinks there's another reason for missing school.

Dr. Schwimmer: “Many of these children are experiencing an awful lot of teasing on a regular basis.”

And as opposed to cancer, Schwimmer says obese children carry a lot of guilt, blaming themselves for being overweight.

Dr. Schwimmer: “This is something that happened when they're five years old. How can that be their fault?”

But the terrible reality for Nanette, Justin, and TJ is that now that they're teens, the chance they can ever be normal is very small. Frankly, some experts make it sound impossible. They say childhood obesity is 100 percent preventable, but almost 100 percent incurable. Evidence, both medical and statistical, suggests these kids are doomed to a struggle they are almost certain to lose.

In fact, in a growing number of extreme cases, hospitals are turning to a solution once unheard of for teens: stomach stapling.

Morrison: “Have you ever considered surgery?”

Nanette: “Yeah. Sometimes I do. Like sometimes when I'm just sick of being fat I'm like, ‘Oh, my goodness, why can't this go away?’ I think like, ‘Well, if I got this and maybe it would help.’"

Morrison: “Is it a serious option?”

Nanette: “Yeah.”

So if childhood obesity is all but incurable, if surgery is a real option, what are the teens doing at camp? The simple reason is that they believe. Nanette is determined to lose the weight herself. So are Justin and TJ. But remember, this is their third year at camp.

TJ: “The first two years I lost and gained, lost and gained.”

Will they finally succeed this year?

TJ: “Yeah, I really think I can. I hope I can. I really do wish I can.”

Nanette: “Yeah, I think I'm more mature this year and so I'm thinking, well, this is going to benefit me, no one else.”

June 22, 2003: Camp begins
Justin, TJ, and Nanette land at the Camp La Jolla, a fitness program just north of San Diego. Frequent flyers of sorts, it’s their third summer in a row there. In the past they've lost the weight, only to gain it back during the school year. It’s a frustrating process, and at up to $8,000 a summer, a pricey one. But this year, we'll be watching for two months in camp and then six months back home.

Justin: “My goal for the entire summer is about 260. I'd like to get down to about 260.”

At first day measurements, Justin is big all over, six-foot-five and a whopping 350 pounds. Can he really lose 90 pounds in nine weeks? TJ, Justin's bunkmate, at 316 and six-foot-four, hopes to shed about 65 pounds. As for Nanette, she wants to lose 30 pounds.

It sounds less ambitious, but that's almost a pound lost every other day. At five-foot-four, she weighs 304 pounds when she arrives at camp.

How will they do it? It will take fitness, sports, and exercise. For six hours or more every day, in a non competitive environment, they will find activities they enjoy, perhaps for the first time in their lives. They've certainly never been so active before.

As for the diet, it is rigid, but balanced, set by dieticians at 1,200 calories for girls, 1,500 for boys. That's less than half of what they'd normally eat a day. Sometimes much less than half.

As we watch, they shrink. There's obviously a long way to go, but early results are almost instantaneous. After just a week, Nanette has lost seven pounds. So did TJ. Justin lost 10 pounds. Jason Eggerman has been the boys' counselor for the past three years.

Jason Eggerman: “He looked at the scale and he said, who's your daddy? Right to the scale. So that was pretty exciting for him to be able to say he lost 10 pounds in a week.”

And, in what can be even more rewarding than weight loss, they are, for once, not outcasts. Some find the first real friends of their lives.

Nanette: “You're around people that understand the same thing that you're going through and you can talk to them about it and they'll like help you.”

And for once, they can even perform in a talent show without fear of humiliation from an audience of snickering and thinner peers.

Justin: “The big one they push is portion control. Because you know a super size fries got like seven portions in it or something.”

In the culinary history of America, many say the 1990s will go down as the "super-sizing decade," when portions of fast food and processed food ballooned because of competition and cheaper production methods.

Morrison: “When you saw what a portion size actually is—“

Justin: “Wow, it was heart-wrenching, man. You know, 12 chips. God, I could rip through 12 in no time.”

July 21: Second weigh in
A month into camp, there's a second weigh in. Nanette is right on target, losing steadily almost a pound a day. But something strange has happened to the boys. Both had been losing about 10 pounds a week, but by the second weigh in, TJ has lost only four pounds in a week, while Justin has lost two.

Now summer is half-gone and they're getting anxious now about reaching their goals -- and about what's waiting for them on the outside.

TJ: “My biggest fear is that I'll go back to the lifestyle I once led. That's like my biggest fear…

Go out binge eating and just eat as much as I can. That's really what I'm scared of. It's-- I don't want to do that again. I really don't. I don't want to be big anymore.”

With that in mind, halfway through camp, parents are invited for a weekend retreat. Parents are told that if they want their kids to continue losing weight, they must be totally committed and involved once their children are back home, and that will be difficult.

Justin's parents, who have flown in from Oklahoma to be there, know the difficulty well.

One parent is absent from the weekend retreat: TJ's mother. For most of his life, she's been more buddy than parent, but lately, she's been neither. TJ can't understand it. But then, finally, she does call -- and what she says is a bombshell. Over the phone, she tells TJ she is leaving, moving to Arizona with her second husband. TJ will have to fend for himself in California, hopefully living with relatives. And now TJ, a 17-year-old heading to senior year in high school, is an angry and grief-stricken mess.

Morrison: “Do you worry about how much you need your mother?”

TJ: “Yeah, I worry about it. You know, I wish she could always be there.”

Morrison: “There are a lot of women who would kill to have a son say that about them. I'd wish she'd always be there.”

Final weigh inTwo weeks before camp is over there's another weigh in. Despite the exercise and diet, there is more bad news. TJ, who has not lost any more weight, redoubles his efforts. Still about 300 pounds, he is far from his goal of 250 and time is running out. But the issue, the one he can't seem to resolve, is this: Will the chaotic life he's facing once camp is over help him succeed or do him in?

Justin, TJ, and Nanette have worked hard for nine weeks. They exercised at least six hours a day, ate very little, and spent nights planning how to avoid all those food temptations that do them in every year. They are certainly not leaving the camp thin. Having begun at over 300 pounds, they have a long way to go, but they believe they received the tools, and encouragement, to continue. And as they discover in their final weigh in, they did lose a lot of weight.

Nanette's goal was less ambitious than the boys, but she meet it. The last night of camp, there's a ceremony and awards. Neither boy reached his goal, but both lost a lot of weight.

Justin: “I lost 50 pounds over the whole summer. So, you know, you try to relate it to things you know, and I lost basically a sack of feed. I think my chances of keeping the weight off this year are good. I feel like I can do it.”

TJ: “I lost 35 pounds total, in my nine weeks stay. I would like to be like 260, 270. That was my goal. But it's all right, 280's cool, I'm almost there. I can lose the rest at home.”

Dateline wires the home of a volunteer, Jenny, from top to bottom with hidden cameras. Then she called repairmen to her house for a simple problem we created as a test with Jenny's pool. NBC's Chris Hansen reports.